Backport of #10123, #9967, and #9972 to `core/1.42`
Includes three cherry-picks in dependency order:
1. #9972 — `fix: resolve all lint warnings` (clean)
2. #9967 — `test: harden subgraph test coverage and remove low-value
tests` (clean)
3. #10123 — `test: subgraph integration contracts and expanded
Playwright coverage` (1 conflict, auto-resolved by rerere from #10326)
See #10326 for core/1.41 backport with detailed conflict resolution
notes.
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Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: bymyself <cbyrne@comfy.org>
Co-authored-by: GitHub Action <action@github.com>
